The present invention relates to the general field of turboprops comprising at least one set of variable orientation fan blades. It relates more particularly to orientation control of the fan blades of a dual propeller aircraft turboprop.
In known fashion, a dual propeller aircraft turboprop includes a turbine with two counter-rotating rotors each driving one set of unducted fan blades. Reference can be made for example to document GB 2,129,502 which describes different embodiments of such a turboprop.
In this kind of turboprop, the orientation of the fan blades of each set (the term pitch control is also used) constitutes one of the parameters making it possible to control the thrust of the turboprop.
Different solutions have been proposed for controlling the fan blades of a given set. Reference can be made for example to French patent applications No. 09 53589 and 09 53591 filed by the Applicant on 29 May 2009. In these applications, provision is made for coupling the blades, for the purpose of adjusting their orientation, to a synchronization ring moved in rotation by means of a central cylinder and connecting arms.